[unreadable] Broad long-term objectives: To develop methods of measuring regional pulmonary gas flow and volume using hyperpolarized 3He MRI. Health Relatedness: Small airway disease is responsible for considerable morbidity and mortality. Current methods of assessing lung disease are either global rather than regional or reveal lung anatomy rather than function and are therefore often of limited use, particularly in assessment of small airway disease. This project will develop a potentially much more sensitive method of assessing regional lung function. Specific Aims: 1) To develop methods of dynamic image co-registration to project images acquired at different points in the breathing cycle onto a single reference frame. 2) To adapt algorithms based on indicator dilution theory to the measurement of gas flow. Research Design: 1) A combination SPAMM tagged proton MRI and spirometry will be used to measure lung position during the respiratory cycle. Affine transformations will then be applied to map lung positions to a reference image frame. 2) Dynamic spiral 3He MRI will be performed during inhalation of hyperpolarized 3He. Standard indicator dilution algorithms will be applied to the dynamic 3He images to calculate gas flow and volume on a pixel by pixel basis. [unreadable] [unreadable]